I want to throw in here that just because something is underused doesn't mean it's broken.
Damage pulse is a good example. Most people don't use the primary because melee isn't particularly useful in space, but as fleets and AI improve, it may be viable to build drone swarms that ram ships and pulse them. Pulse has a very large radius and high damage, which potentially makes it devastating in large numbers against armor. It's just not meant for >100m ships that can't maneuver well enough to use it. As a secondary, it's for high alpha. High alpha isn't too popular in starmade, but to explain:
Imagine you have space for a 1500 module weapon. You already have a fairly standard main gun (maybe it's cannon/cannon/explosive or something), so you think "hey, maybe an ion weapon for plowing through shields". You could go beam/cannon/ion - this gives you 30,000 dps (1500 blocks * 10 dps/block * 2x ion modifier). This is nice, but only useful if your target has less than 30,000 regen; otherwise you make no progress.
On the other hand, you could go with beam/pulse/ion - this is still only 30,000 dps, but a slightly insane 1,500,000 burst damage (30,000 dps * 5 second base burst time * 10x pulse modifier). This means that if your target has less than 1.5m shields, it doesn't actually matter how much regen they have; you can one shot their shields. The point of high alpha is that even if you can only fire once, you only NEED to fire once. Just, you know, don't miss.
Back to the original point, just because beam/pulse/ion is underused doesn't mean it's fundamentally broken (or, more importantly, that it needs a buff, because it doesn't). Your ability to make a unique ship that uses an underused (but not underpowered) weapon combination is an important check for the current meta. You might think you're totally fine flying around with 500k shields and 50k regen because you're used to people using pure DPS weapons to take you down - my ability to shatter that expectation is very important. It also helps keep combat a little less linear - just because you're bigger than me, doesn't mean you're going to win in a fight. I have unique tactical options I can use to turn the tables in my favor.
Plus, who doesn't like missile/pulse/explosive? Like, sure, the range and speed suck, but that 40m radius hole is SO worth it.
As for decorative blocks, I definitely think there's intrinsic value in things people don't use very often (like plants or green hazard stripes). Art would be really boring if everyone only used 3 colors or only ever painted 3 things. You never know what might look good - ice was a useless block until someone figured out that putting it in front of a light source looks really cool.